16 Water/Wastewater
Dynamic Process Control with ISE Sensors Decreases Energy Costs
Optimising the degradation processes in a SBR wastewater treatment plant
The Glückstadt municipal wastewater treatment body (SEG) near Hamburg, Germany, first operated an aeration plant and combined sludge stabilisation with a size of 36,000 population equivalent (PE). In the course of the plant modernisation, rebuilding to a Sequencing Batch Reactor (SBR) plant with a capacity of 20,000 PE was carried out in 2004 (Figure 1).
Glückstadt wastewater treatment plant: Overview of the plant and procedure
The wastewater first runs through screens and sand catcher systems and is then temporarily stored in a storage basin. For further cleaning, it passes alternatingly into one of the two SB reactors. Finally it is temporarily stored in an outflow reservoir, before being directed into the River Elbe.
Figure 1: Aerial photo of the Glückstadt wastewater treatment plant
We are very pleased with the new measuring technology which allows us to keep the discharge values stable and at the same time save energy.
The plant has no digestion tower; centrifuges dewater the excess sludge which is usually used in agriculture. An overview of the wastewater treatment plant is shown in Figure 2.
The two SB reactors each have a total volume of 4500 m3 and each
reactor cleans 750 m³ wastewater per cleaning cycle. Two blower units of 75 kW are available per reactor. The fixed time individual phases of the SBR operation of the Glückstadt wastewater treatment plant are based on several years of experience (Table 1).
The entire cleaning cycle per reactor is approx. 10 hours.
If necessary, e.g. during strong rainfall, the fixed times can be overridden manually. However, manual plant management requires the presence of additional, particularly experienced operating personnel. This is associated with considerable extra organisational effort, especially at night and on weekends.
The SB reactors measuring system includes an IQ SENSOR NET system (Figure 3) and optical oxygen sensors FDO (Figure 4). Up to the introduction of the dynamic control of the SBR process, only the oxygen measurement was used as a control variable, whereby the
oxygen input was by means of frequency-controlled blower units in order to keep the oxygen concentration constant during the nitrification phases.
First test measurements with ISE sensors
The aim of our 2008 measurement campaign was to find out whether the fixed times of the nitrification and denitrification phases still fit to
SBR phase Phase 1
Phase 2 Phase 3
Phase 5 Phase 6 Phase 7
Phase 8 Phase 9 Process
Filling 1 (500 m3 & denitrification
)
Denitrification 1 / Bio-P
Nitrification 1
Phase 4 Filling 2 (250 m3 denitrification
) &
Denitrification 2 Nitrification 2 Sedimentation
Clarified water discharge (750 m3
& surplus sludge withdrawal
Pause Table 1: Fixed time phases of SBR operation with simple O2 control strategy. ) Time period 60 min 45 min
110 min 30 min 75 min
120 min 130 min
40 min Active components
Filling pumps / Stirrer
Stirrer Aerator units
Filling pumps / Stirrer
Stirrer Aerator units
Decanting / Pumps
Author Details: Thomas Mangels Sperforkenweg 6–8
25348 Glückstadt, Germany E-Mail:
Thomas.mangels@stadtent-
waesserung-glueckstadt.de
Figure 2: Block diagram of Glückstadt wastewater plant IET Annual Buyers’ Guide 2013
www.envirotech-online.com
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